In general, a permalloy A (Fe-70 to 80% Ni) (% denotes percent by mass, which is the same hereinunder) is known, as a high permeability soft magnetic material as an ingot material and a sintered material. After applying heat treatment to this material, if it is annealed, an FeNi3 order phase is generated and the crystalline magnetic anisotropy constant K1 becomes negative with a large absolute value. It is known that: if the crystalline magnetic anisotropy constant K1 is negative, the <111> direction becomes the easy magnetization direction and the <100> direction becomes the hard magnetization direction; if it is positive, the <100> direction becomes the easy magnetization direction and the <111> direction becomes the hard magnetization direction; and if it is zero, the crystalline material becomes magnetically isotropic. Due to the generation of this FeNi3 order phase, magnetic anisotropy is generated, resulting in a decrease in the magnetic permeability in a normal polycrystalline substance where the crystal face is not oriented, and which is isotropic in the crystal orientation. To obtain a high magnetic permeability in this material requires quenching after high temperature heat treatment, and further an aging treatment thereafter. However, such processing is not industrially used.
Moreover, there is known a Mo permalloy (Fe-79% Ni-4%-Mo) and a supermalloy (Fe-79% Ni-5% Mo), that are permalloys added with Mo. Due to the addition of Mo, even if these materials are annealed after heat treatment, generation of the FeNi3 order phase is suppressed, and even if quenching is not applied after heat treatment, the crystalline magnetic anisotropy constant K1 becomes about zero, showing a superior magnetic permeability in a polycrystalline substance which is isotropic on the crystal orientation. Therefore, these materials are widely used industrially. Moreover, in order to further improve the magnetic permeability, a high permeability soft magnetic material added with Cu, Cr, and Mn in addition to Mo is known.
Meanwhile, there is known that a soft magnetic flaky powder is obtained by flattening powder having a similar composition. For example, a soft magnetic flaky powder is known, which has the composition of Fe-70 to 83% Ni-2 to 6% Mo-3 to 6% Cu-1 to 2% Mn, an average particle size of 0.1 to 30 μm, and an average thickness of 2 μm or less. The soft magnetic flaky powder is used, for example, as a soft magnetic flaky powder for a magnetic card (refer to Japanese Unexamined Patent Application, First Application No. Hei 03-223401).
Moreover, there is known soft magnetic flaky powder having a composition of Fe-40 to 80% Ni-2 to 6% Mo. This soft magnetic flaky powder is used, for example, as a flat soft magnetic powder for magnetic marking (refer to Japanese Unexamined Patent Application, First Application No. Hei 03-232574).
Furthermore, a soft magnetic flaky powder is known, which has a composition of Fe-60 to 80% Ni—Mo or Fe-60 to 80% Ni-5% or less Mo. This soft magnetic flaky powder is used, for example, as a high frequency magnetic core (refer to Japanese Unexamined Patent Application, First Application No. Hei 04-78112).
In any of such conventional Fe—Ni—Mo soft magnetic flaky powders, it is known that the magnetic property such as the magnetic permeability in the flat surface of the powder can be further increased by flattening the Fe—Ni—Mo powder obtained by normal crushing or atomization for generating shape magnetic anisotropy due to the demagnetizing field, so as to make the easy magnetization face be within the flat surface.
Such conventional Fe—Ni—Mo soft magnetic flaky powders are all manufactured such that the Fe—Ni—Mo powder obtained by normal crushing or atomization is added with ethanol or water as a solvent, and further added with pulverizing agent as required, which is then flattened using an attritor or a ball mill.
The thus obtained Fe—Ni—Mo soft magnetic flaky powder is used to form a magnetic composite material by dispersing the flat soft magnetic powder in the resin such that the flat face is oriented in one direction. In a case that the magnetic composite material is a magnetic composite sheet, the flat surface of the Fe—Ni—Mo soft magnetic flaky powder is oriented in the right angle direction with respect to the thickness direction of the magnetic composite sheet.
However, there is a problem that the conventional Fe—Ni—Mo soft magnetic flaky powder does not exhibit sufficient properties as a high frequency magnetic material for use as a radio wave absorber having a radio wave absorption property at several tens MHz to several GHz, or for use as an antenna core for wireless communications having the magnetic property at several tens kHz to several tens MHz. Therefore, it is desired to obtain a soft magnetic flaky powder having more superior magnetic permeability in the flat surface.